1. Field of the Invention
The invention relates to an oil reservoir or sump for an automatic transmission mechanism in an automotive vehicle powertrain.
2. Background Art
An automatic power transmission mechanism in a contemporary automotive vehicle powertrain includes a gear system, typically a planetary gear system with multiple gear ratios, fluid pressure actuated friction clutches and brakes to establish and disestablish torque flow paths through the gearing, and a hydrokinetic torque converter including an impeller connected to the crankshaft of an internal combustion engine and a turbine connected drivably to the torque input element of the gear system. A positive displacement transmission pump in a transmission housing has a pump driving element connected to the impeller. When the engine is operating, the pump establishes control pressure for fluid pressure actuators for the friction clutches and brakes as well as lubrication oil pressure.
A transmission reservoir or sump typically is connected to the transmission housing at a location below the transmission gearing for storing transmission fluid. The sump is in fluid communication with an inlet side of the impeller driven transmission pump.
The transmission includes a control valve system, which is supplied with control pressure fluid from the transmission pump. Drainage ports in the valve system allow control pressure fluid to return to the transmission sump where it is filtered and recirculated.
Normal maintenance of the transmission requires the transmission fluid sump to be drained and refilled periodically. Typically, a drum plug and fill pipe assembly is used for the purpose of draining and filling the sump. Other known transmission designs make use of a fill port above the sump and a dip stick to ascertain the level of fluid in the sump. If a transmission fluid drain plug and fill pipe assembly is used, the length of the fill pipe determines the fluid level of the transmission fluid in the sump. A drain plug is integrated with the fill pipe. That design may result in multiple potential fluid leak paths at the sealing interface of the fill pipe with the sump and at the interface of the fill pipe and the plug.
Threaded connections are used with a conventional drain plug and fill pipe assembly for securing the fill pipe to the sump and for securing the plug to the fill pipe. Recommended torque limits for these elements are established for each threaded connection. Typically, the torque limits determine overlapping torque windows for the threaded connections. A torque applied to one element, therefore, may be inconsistent with the recommended torque for the other element. Further, any corrosion at either of the threaded connections will cause differences in the degree of overlap of the two torque windows. Further, known designs of this type have multiple sealing interfaces, each interface creating a potential fluid leak path.